Tropical Storm Arthur bears down on the coast of Florida, in this photo captured today (July 2) by astronauts aboard the International Space Station.

The menacing storm is clambering northward, and could strengthen into the first hurricane of the season by Friday, just in time to spoil Fourth of July festivities along the U.S. East Coast. The U.S. National Hurricane Center (NHC) warns that the storm could hit the coast of North Carolina tonight or Thursday, before intensifying into a Category 1 hurricane by Friday.

As of the NHC's latest update, issued at 5 p.m. EDT (2 p.m. PDT), Tropical Storm Arthur was located 220 miles (355 km) south-southeast of Charleston, South Carolina.

A hurricane warning has been issued for the North Carolina coast, and the NHC reports that the storm is moving north at approximately 7 mph (11 km/h), with winds traveling nearly 70 mph (110 km/h). The hurricane warning is in effect across the entire coast of North Carolina, stretching all the way north to the Virginia border.

North Carolina Gov. Pat McCrory has declared a state of emergency for 25 coastal and inland counties, and has urged people to exercise caution in the coming days.

"While we all want to enjoy a fun Fourth of July weekend with friends and family, our highest priority should be safety during the storm," McCrory said in a statement. "I encourage all of our coastal residents and visitors to take necessary precautions, listen to local media and use good judgment throughout the duration of the storm."

The North Carolina Emergency Operations Center is monitoring the storm, and the State Emergency Response Team will remain on standby as the situation develops.

"While the current forecast does not indicate Arthur will cause major damage, we are taking this storm very seriously," Emergency Management Director Mike Sprayberry said in a statement. "Emergency management personnel, in conjunction with our federal, state and local partners, are ready to support the counties in preparation, response and recovery efforts as needed."

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Denise Chow

Denise Chow is the Sci-Tech Editor at Live Science. Before joining the Live Science team in 2013, she spent two years as a staff writer for Space.com, where she wrote about rocket launches and covered NASA's final three space shuttle missions. A Canadian transplant, Denise has a bachelor's degree from the University of Toronto, and a master's degree in journalism from New York University.